Meterable fibrous material

ABSTRACT

A particle or particles of cellulosic wood pulp fibers having a top and bottom face and a hexagonal perimeter, and methods of using it.

This relates to a cellulosic wood pulp in meterable form.

Cellulose wood pulp fibers can be used as a filler and/or reinforcementand/or property modifier in many materials. There is a need to be ableto meter the amount of fiber being placed in the material so that thereis a more even amount of fiber throughout the material.

As an example in the plastics industry, fillers and reinforcementmaterials are typically used to improve the properties of plastics. Theaddition of such materials can improve properties such as conductivity,strength, modulus values, notched impact resistance, density,absorbency, etc.

A partial list of plastic or polymeric materials which utilize fillersor reinforcing materials includes polyolefins, polyethylene,polypropylene, polyvinyl chloride, ABS, polyamides, mixtures of these,polyethylene terephthalate, polybutylene terephthalate,polytrimethylterephthalate, ethylene-carbon monoxide and styrenecopolymer blends such as styrene/acrylonitrile and styrene/maleicanhydride thermoplastic polymers, polyacetals, cellulose butyrate,acrylonitrile-butadiene-styrene, certain methyl methacrylates, andpolychlorotrifluoroethylene polymers.

Fibrous materials are used as reinforcements in plastics. Glass fibersare used as a reinforcing component for plastics. Glass fibers are usedas a reinforcement material for both thermoset plastics andthermoplastics. Glass fibers are used to impart mechanical strength,dimensional stability, and heat resistance to the product. Glass fibers,however, increase the density and weight of the product, are costly, andare abrasive, abrading the processing equipment.

Mineral fibers are another material used as a filler and forreinforcement. They also are dense and add to the weight of the product.They are also abrasive.

Cellulosic wood pulp fibers do not have these disadvantages. Cellulosicwood pulp fibers have relatively low densities as compared to glassfibers or mineral fillers. For example, cellulose wood pulp fibers havea density of approximately 1500 kg/m³ in comparison to a density of 2500kg/m³ for E grade glass fibers. This provides a product that is lessdense and weighs less. This is an important consideration in manyapplications including, for example, automotive applications. Cellulosicwood pulp fibers are not as abrasive as glass fibers and do not abradethe processing equipment to the same extent as glass fibers or mineralfillers.

Cellulose wood pulp fibers can be used as reinforcing and filler inthermoset or thermoplastic materials, as reinforcing in fiber-cementmaterial, combined with more dense material as a densification modifierto make the combined product less dense and have less weight, andcombined with other materials to make them more absorbent or to absorbat a faster rate.

In each of these uses it is necessary to have an understanding of theamount of fiber that is being added and for the fiber to be added in auniform manner. It would be beneficial to have a cellulosic wood pulpfiber that is in a form that would allow it to be easily and uniformlymeterable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an embodiment of the invention.

FIG. 2 is a side plan view of the embodiment of FIG. 1

FIG. 3 is an isometric view of the embodiment of FIGS. 1 and 2.

FIG. 4 is a top plan view of another embodiment of the invention.

FIG. 5 is a side plan view of the embodiment of FIG. 4

DESCRIPTION

The present invention can utilize a number of tree species as the sourceof the pulp, paperboard and paper fibers. Coniferous and broadleafspecies and mixture of these can be used. These are also known assoftwoods and hardwoods. Typical softwood species are various spruces(e.g., Sitka Spruce), fir (Douglas fir), various hemlocks (Westernhemlock), tamarack, larch, various pines (Southern pine, White pine, andCaribbean pine), cypress and redwood or mixtures of same. Typicalhardwood species are ash, aspen, cottonwood, basswood, birch, beech,chestnut, gum, elm, eucalyptus, maple oak, poplar, and sycamore ormixtures thereof. Recycled cellulosic material can be used as startingmaterial for the fibers. The present invention can use chemical,mechanical, thermomechanical and chemithermomechanical pulp. Kraft,sulfite and soda chemical pulps can be used. The fibers can be bleachedor unbleached. The present invention can be used with unbleached Douglasfir chemical pulp fibers.

The use of softwood or hardwood species may depend in part on the fiberlength desired. Hardwood or broadleaf species have a fiber length of 1-2mm. Softwood or coniferous species have a fiber length of 3.5 to 7 mm.Douglas fir, grand fir, western hemlock, western larch, and southernpine have fiber lengths in the 4 to 6 mm range. Pulping and bleachingmay reduce the average length slightly because of fiber breakage.

In the manufacture of pulp woody material is disintegrated into fiberseither in a chemical or mechanical type process. The fibers can thenoptionally be bleached. The fibers are then combined with water in astock chest to form a slurry. The slurry then passes to a headbox and isthen placed on a wire, dewatered and dried to form a pulp sheet.Additives may be combined with the fibers in the stock chest, theheadbox or both. Materials may also be sprayed on the pulp sheet before,during or after dewatering and drying.

Traditionally, pulp has been added to other materials either in sheet,bale or fibrous form after the pulp sheet or bale has been comminuted orslurried. It would be advantageous to have pulp in alternative form,such as particles, that could be metered in metering devices well knownin the art. In the present invention it has been found that cellulosicwood pulp fibers can be made into particulate form and the shape ofthese particles will determine the speed and uniformity by which thefiber can be metered and processed. A particle having a hexagonal shapecan be fed faster and more uniformly than a particle having a squareshape.

In one embodiment the particles are placed in a metering system. Theparticles are placed in a volumetric or weight loss system and meteredand conveyed to the next process step. In one embodiment a single ortwin screw feeder is used to meter and convey the particles into thenext process step. The next process step will depend on the materialwith which the particles are being mixed. The material can be athermoset or thermoplastic material, an aqueous solution for cement suchas portland cement or a dry material such as clay or loam. In someembodiments the particles will be formed into fibers, fiber bundles or amixture of fibers and fiber bundles before or during the mixing. Inother embodiments the particles may substantially remain as particlesduring the mixing.

A partial list of plastic or polymeric materials which can utilize thecellulose wood pulp fibers can include polyolefins, polyethylene,polypropylene, polyvinyl chloride, ABS, polyamides, mixtures of these,polyethylene terephthalate, polybutylene terephthalate,polytrimethylterephthalate, ethylene-carbon monoxide and styrenecopolymer blends such as styrene/acrylonitrile and styrene/maleicanhydride thermoplastic polymers, polyacetals, cellulose butyrate,acrylonitrile-butadiene-styrene, certain methyl methacrylates, andpolychlorotrifluoroethylene polymers. A complete list of thermoset orthermoplastic material which can utilize cellulose wood pulp fiber isknown to those skilled in the art.

Cellulosic wood pulp fibers can be in the form of commercial cellulosicwood pulps, bleached board and paper. These materials are typicallydelivered in roll or baled form. The thickness of the pulp sheet, paperor board (the fiber sheet) is one factor that can determine thethickness of the particle. The fiber sheet has two opposed substantiallyparallel faces and the distance between these faces will be thethickness of the particle. A typical fiber sheet can be from 0.1 mm to 4mm thick. In some embodiments the thickness may be from 0.5 mm to 4 mm.One of the other factors affecting the particle thickness is thepresence of any pretreatment to the fiber sheet. Thus the particle canbe thicker or thinner than the fiber sheet.

The fiber sheet, and the particles, can have a basis weight of from 12g/m² (gsm) to 2000 g/m². In one embodiment the particles could have abasis weight of 600 g/m² to 1900 g/m². In another embodiment theparticles could have a basis weight of 500 g/m² to 900 g/m². For a papersheet one embodiment could have a basis weight of 70 gsm to 120 gsm. Inanother embodiment a paperboard could have a basis weight of 100 gsm to350 gsm. In another embodiment a fiber sheet for specialty use couldhave a basis weight of 350 gsm to 500 gsm.

Pulp additives or pretreatment may also change the character of theparticle. A pulp that is treated with debonders will provide a looserparticle than a pulp that does not have debonders. A looser particle maydisperse more readily in the material with which it is being combined.

The particle has a hexagonal shape, one embodiment of which is shown inFIG. 1. The hexagon can be of any type from fully equilateral to fullyasymmetric. If it is not equilateral, the major axis may be from 4 to 8millimeters (mm) and the minor axis may be from 2 to 5 mm. Some of thesides of the hexagon may be of the same length and some or all of thesides may be of different lengths. The circumference or perimeter of thehexagon may be from 12 mm to 30 mm and the area of the upper or lowerface 24 or 26 of the particle may be from 12 to 32 mm². In oneembodiment the particles could have a thickness of 0.1 to 1.5 mm, alength of 4.5 to 6.5 mm, a width of 3 to 4 mm and an area on one face of15 to 20 mm². In another embodiment the particles could have a thicknessof 1 to 4 mm, a length of 5 to 8 mm, a width of 2.5 to 5 mm and an areaon one face of 12 to 20 mm².

Two examples of a hexagonally shaped particle are shown.

In FIGS. 1-3, particle 10 is hexagon shaped and has two opposed sides 12and 18 which are equal in length and are longer than the other foursides 14, 16, 20 and 22. The other four sides 14, 16, 20 and 22 may bethe same length, as shown, or the four sides may be different lengths.Two of the sides, one at each end such as 14 and 20 or 14 and 22 may bethe same length, and the other two at each end, 16 and 22 or 16 and 20,may be the same length or have different lengths. In each of thesevariations, the sides 10 and 18 may the same length or of differentlengths. The edges of the particles may be sharp or rounded.

The distance between the top 24 and bottom 26 of particle 10 may be from0.1 mm to 4 mm.

FIGS. 4 and 5 illustrate an embodiment in which each of the six sidesthe hexagon is of a different length. The embodiment shown isillustrative and the order of the lengths of the sides and size of thelengths of the sides can vary.

Particles of the shape, size and basis weight described above canreadily be metered in weight loss and volumetric feeder systems wellknown in the art.

The alignment of the fibers within the particle can be parallel to themajor axis of the hexagon or perpendicular to the major axis of thehexagon or any orientation in between.

The hexagonal particles can be formed on a Henion dicer, but other meanscould be used to produce a hexagonal particle.

The hexagonal particles have a number of advantages over square orrectangular particles. A particle with a hexagonal circumference can beproduced faster than a particle with a rectangular or squarecircumference and can be metered faster than a particle with arectangular or square circumference. In one embodiment, hexagonalparticles are produced at 1.6 times the rate of square particles.

As an example of the benefits provided by hexagonal particles, a CF 405pulp from the Weyerhaeuser NR Company, Columbus, Miss. mill was formedinto a hexagonal particle 6.14 mm (˜¼ inch) on the long axis and 3.36 mm(˜⅛ inch) on the short axis, a 3/32 inch (2.38 mm) square particle and a⅛ inch (3.18 mm) square particle. The particles were metered throughboth a twin screw and single screw feeder. Standard vibration agitationas routinely practiced in the art was used to prevent bridging. Therotational speed range was the same for the three particles for eachtest. The amounts fed through the twin screw feeder in pounds/hour/rpmwere 1.61 for the hexagonal particles, 1.16 for the 3/32″ squareparticles and 0.905 for the ⅛″ square particles. The amounts fed throughthe single screw feeder in pounds/hour/rpm were 1.73 for the hexagonalparticles, 0.45 for the 3/32″ square particles and 0.65 for the ⅛″square particles.

The invention claimed is:
 1. A cellulosic wood pulp fiber particlehaving two opposed faces and a hexagonal perimeter, a major axis lengthof 4 to 8 mm, a width of 2 to 5 mm and a thickness of 0.1 mm to 4 mm,wherein the wood pulp fiber is in the form of a wood pulp sheet, apaperboard sheet, or a paper sheet, wherein the particle has a basisweight of 70 to 120 g/m².
 2. A cellulosic wood pulp fiber particlehaving two opposed faces and a hexagonal perimeter, a major axis lengthof 4 to 8 mm, a width of 2 to 5 mm and a thickness of 0.1 mm to 4 mm,wherein the wood pulp fiber is in the form of a wood pulp sheet is inthe form of a wood pulp sheet, a paperboard sheet, or a paper sheet,wherein the particle has a basis weight of 100 to 350 g/m².
 3. Acellulosic wood pulp fiber particle having two opposed faces and ahexagonal perimeter, a major axis length of 4 to 8 mm, a width of 2 to 5mm and a thickness of 0.1 mm to 4 mm, wherein the wood pulp fiber is inthe form of a wood pulp sheet is in the form of a wood pulp sheet, apaperboard sheet, or a paper sheet, wherein the particle has a basisweight of 350 to 500 g/m².